In digital wireless communication systems, adaptive array antenna (hereinafter “AAA”) techniques are used to adaptively control directivity by multiplying weight to an antenna output from a plurality of antenna elements. AAA techniques utilize a direction of arrival of a signal is different from one another and suppress interference signals by adaptively controlling directivity. For this reason, adaptive array antenna techniques are suitable for removing interference signal on a single channel.
In digital wireless communication, there are cases where AAA transmission is performed using the weight used upon AAA reception. In terms of AAA transmission, there is also a method whereby a direction of arrival is estimated in respect to a signal from a user and the weight is calculated so as to turn the directivity in this direction, and AAA transmission is performed using the calculated weight.
Upon performing AAA transmission, channel estimation takes place using the reference signals transmitted by directivity transmission. In this context, an individual pilot channel S-CPICH (Secondary-Common Pilot Indicator CHannel) signal is used per user as a reference signal.
In order to transmit large-volume packet data on downlink channels, the implementation of shared channels such as the DSCH (Downlink Shared Channel) whereby a plurality of communication terminals (users) use one channel has come under consideration in recent years. For instance, when performing transmission using the DSCH, each user uses its dedicated channel to transmit control data to control transmit power and maintain synchronization, while receiving information as to whether the transmitted DSCH signal addresses the user as well as information on the transmission rate of DSCH.
Furthermore, a communication terminal receives dedicated channels and makes decisions as to whether these channels address the terminal apparatus, and, when they do, interprets the information regarding the transmission rate of DSCH from the dedicated channels and receives and demodulates the signals transmitted by DSCH.
Where transmission diversity of CDMA/FDD (Frequency Division Duplex) of 3GPP (3rd Generation Partnership Project) is employed, that is, where transmission diversity and AAA transmission are applied to DSCH, CPICH is transmitted from two pairs of array antennas by means of AAA, which necessitates CIPCHs by double the number of users. As a result, code resources run short and the number of users is limited.